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Title:

Investigation into Locking Point of Asphalt Mixtures Utilizing Superpave and Marshall Compactors

Accession Number:

01663303

Record Type:

Component

Abstract:

Locking point is an important concept for selection of proper aggregate gradation in asphalt mixture design. Locking point is defined as a moment/point during asphalt mixture compaction when a stable aggregate structure is just formed. Further compaction effort does not contribute much to the increase in mixture density or even damage aggregate particles. This study employed two compaction methods, Superpave Gyratory Compactor and Marshall compactor, to investigate the locking points of different asphalt mixtures. For Marshall compaction method, an accelerometer was attached to the Marshall hammer to record response of asphalt. For Superpave gyratory compaction, the changes of compacted samples in height and density were utilized. A total of ten mixtures were designed and evaluated. All the mixtures were prepared with the same asphalt binder PG 64-22 and aggregates. The aggregates were pre-screened by different sieves to control variability in gradation. Results show that it was feasible to determine locking point for most of the mixtures by utilizing an accelerometer, except for one mix with the largest aggregates, which experienced particle breakage during compaction. Locking point is found to be dependent on the full range of aggregate sizes of a mixture. SMA mixtures with similar gradation in the fine particles showed less variability in locking point. Dense-graded mixtures with smaller maximum aggregate size exhibited lower locking point, which can be attributed to a higher asphalt content that serves as a lubricant. The 4-inch Marshall mold was not adequate for determining locking point for the mixtures with particles larger than 1 inch.

Supplemental Notes:

This paper was sponsored by TRB committee AFK50 Standing Committee on Structural Requirements of Asphalt Mixtures.

Report/Paper Numbers:

18-05533

Language:

English

Authors:

Polaczyk, Pawel
Huang, Baoshan
Shu, Xiang

Pagination:

4p

Publication Date:

2018

Conference:

Transportation Research Board 97th Annual Meeting

Location: Washington DC, United States
Date: 2018-1-7 to 2018-1-11
Sponsors: Transportation Research Board

Media Type:

Digital/other

Features:

References

Subject Areas:

Highways; Materials; Pavements

Source Data:

Transportation Research Board Annual Meeting 2018 Paper #18-05533

Files:

TRIS, TRB, ATRI

Created Date:

Jan 8 2018 11:24AM